This invention relates to a valve apparatus for controlling fluid flow, and in particular, to a valve apparatus for providing proportional control of the fluid flow from an inlet port to an outlet port in a valve body of the apparatus.
In one type of a known solenoid operated valve, a plunger of magnetic material is slidable within the solenoid. A spring or other biasing means urges the plunger into contact with a valve seat. When no current is applied to the solenoid, the valve is maintained closed by the spring. When current flows and the solenoid is energized, a magnetic force acts against the spring to move the plunger away from the valve seat. When the magnetic force exceeds the force of the spring, the plunger moves out of contact with the valve seat into a remote position in which the valve is fully open. A valve of this type has two basic positions, open and closed.
A proportional valve is one in which the flow of fluid varies in proportion to the current supplied to a coil in the solenoid. Such a valve may be desirable for applications in which a gradual variation in flow is preferable to an abrupt change between on and off conditions.
Many designs have been proposed for proportional valves. An example of a known proportional valve is shown in U.S. Pat. No. 4,463,332 (the '332 patent) to W. Everett. The proportional valve in the '332 patent includes a solenoid having an electromagnetic coil and a pole piece. The pole piece is located within the electromagnetic coil, and an armature is located near the pole piece and separated therefrom by a core gap. The pole piece is mounted in the solenoid with a threaded engagement which can be adjusted to adjust the core gap. The armature is held in place by an armature retainer, and a pair of flat springs are held between the armature retainer and the armature. The solenoid in the '332 patent also includes an annular permanent magnet surrounding the coil to create a field of predetermined flux density in the pole piece. The solenoid assembly in the '332 patent is shown coupled to a valve assembly which utilizes a ball valve.
U.S. Pat. No. 4,767,097 to Everett et al discloses a proportional valve somewhat similar to that of the '332 patent, but which utilizes a different ball valve assembly and housing.
Another proportional valve is disclosed in U.S. Pat. No. 6,974,117 to Dzialakiewicz et al., which is hereby incorporated in its entirety herein by reference. This patent discloses a valve apparatus that includes a housing having a valve body with an inlet port and an outlet port. In one embodiment, the valve apparatus includes a valve assembly with an armature, a movable fluid control member, and at least one spring biasing the armature into contact with the fluid control member. The valve apparatus further includes a solenoid assembly having an electromagnetic coil and a pole piece. The pole piece and the armature define a gap that changes proportionally with the amount of current flowing through the electromagnetic coil. Fluid flow from the inlet port to the outlet port proportionally increases or decreases as the gap increases or decreases. The valve apparatus also has a valve seat, and the fluid control member contacts the valve seat to inhibit fluid flow through the apparatus when the electromagnetic coil is not energized.